Imperative programming languages, where the order of execution is implicitly defined by the structure of the source code, almost always use eager evaluation.[why?]

One advantage[clarification needed] of eager evaluation is that it eliminates the need[clarification needed] to track and schedule the evaluation of expressions. It also allows the programmer to dictate the order of execution, making it easier to control when sub-expressions (including functions) within the expression will be evaluated, as these sub-expressions may have side effects that will affect the evaluation of other expressions.

Disadvantages of eager evaluation[clarification needed] are that it forces the evaluation of expressions that may not be necessary at run time, and it may delay the evaluation of expressions that have a more immediate need. In imperative languages, it also forces the programmer to organize the source code for optimal order of execution. Conversely, it allows the programmer to order the source code to control the order of execution.